Issues or Controversies

Working with ancient DNA can be challenging. It can be difficult to find sufficient material to work with after decomposition and fossilization have occurred and to eliminating contamination from modern human DNA. Distinguishing between modern human and ancient genetic material is particularly difficult when the ancient DNA comes from our close relatives.

• Organisms decompose after death. Water, oxygen and microbes break down DNA, which is a very fragile molecule. Therefore ancient DNA tends to be found in small quantities and is generally fragmentary and damaged.
  
• Sometimes is possible to amplify the recovered DNA and obtain a viable sample for analysis. One key factor in harvesting ancient DNA is having technology that allows for the smallest of DNA samples to be detected and collected for study.
• Contamination by modern DNA is a particularly difficult problem to solve. 
  
• Fossils  have been handled by researchers for years and could be contaminated with DNA from hundreds of sources, especially since fossil excavation and subsequent handling does not often require gloves and wearing gloves can actually impede many non-DNA related aspects of fossil study.
  
• Contamination is difficult to detect because Neanderthals and humans share much of their genetic material, making some DNA sequences indistinguishable between the two species. 

There are several genes that our Neanderthal relatives have contributed to our genome that were once beneficial in the past but can now cause health-related problems. One of these genes allows our blood to coagulate, or clot, quickly, a useful adaptation in creatures who were often injured while hunting.

There has been considerable debate about whether Neanderthals had the capability for fully modern speech. The Neanderthals (Homo neanderthalensis) became extinct about 28,000 years ago and it is often claimed that a reduced language ability compared with modern humans may have been a factor in their extinction.Evidence for and against their language ability is based on analyses of their skeletal remains and the artefacts that they left behind. The evidence is  suggesting Neanderthals were competent, complex, social creatures. In light of their apparent cognitive abilities,  that was inclined to believe they had language. But  we can't prove it, and no one else can, either. To date, there's no evidence that Neanderthals developed writing, so language, if it existed, would have been verbal. Unlike writing, spoken languages leave no physical trace behind. Our words vanish as soon as they're spoke. Part of the reason scientists disagree about Neanderthal language is because there are different definitions of language itself. Without straying too far into academic debates over the nature of language, let's just say there are broad and narrow theories when it comes to what actually constitutes language.